I argue that contraception is morally wrong but that periodic abstinence (or natural family planning) is not. Further, I argue that altered nuclear transfer—a proposed technique for creating human stem cells without destroying human embryos—is morally wrong for the same reason that contraception is. Contrary to what readers might expect, my argument assumes nothing about the morality of cloning or abortion and requires no premises about God or natural teleology. Instead, I argue that contraception and altered nuclear transfer are morally wrong because they fail to treat humanity as an inviolable end